| 摘要 |
PURPOSE:To hold oscillation frequency and to reduce leading-in time constant, by fixing the control voltage to be applied to a voltage controlling oscillator to the voltage existing before disconnection of an input signal at the time of disconnection. CONSTITUTION:The output of the voltage controlling oscillator 5 is compared with an input signal 1 by a phase comparator 2 through a frequency divider 4 and the output of the phase comparator 2 is integrated by an integrator 3. A phase synchronizing circuit controlling the voltage controlling oscillator 5 through a sample holding circuit consisting of a switch 7, an accumulator 8 and a transistor 9 is provided with a monostable multivibrator 6 for detection of input signal disconnection. When the input signal 1 is disconnected, the output of the monostable multivibrator 6 is turned to the low level, the switch 7 is opened and the output of the sample holding circuit 11 is fixed on the voltage existing before the disconnection, so that oscillation frequency is held. Consequently the leading-in time constant can be also reduced. The system can be effectively used in case of receiving a clock from an intermittently disconnected transmission line and synchronizing a self-clock with the received clock. |
